First example does not demonstrate covariance

[dtolnay]

The example says:

Here you can see that a non-send/sync inner type doesn't affect the wrapper type, and that the 'static lifetime gets cast into a 'a lifetime.

fn main2() {
    let x: PhantomCovariantAlwaysSendSync<&'static *const ()> = PhantomData;
    fn f<'a>(_: PhantomCovariantAlwaysSendSync<&'a *const ()>) {}
    f(x);
    let _y: &(dyn Send + Sync) = &x;
}

I don't think "'static lifetime gets cast into a 'a lifetime" is accurate. All that's happening is that 'a is being instantiated with 'a = 'static. There is no subtyping or variance at play. The same code works if you write it with PhantomContravariantAlwaysSendSync.